a) Field of the Invention:
The present invention relates to a pump which is used in a hot water supply apparatus or the like for feeding hot water.
b) Description of the Prior Art
An impeller pump is conventionally used as a pump in a hot water supply apparatus such as a jar, a pot or the like for feeding a liquid at a relatively high temperature.
This impeller pump has such a configuration as that shown in FIG. 1, and when the pump is to be used for feeding hot water, a hole 30a is formed in a bottom of a vessel 30 of a hot water supply apparatus to be filled with hot water and a suction port of the pump is connected to the hole. In FIG. 1 which illustrates the configuration of the impeller pump, a reference numeral 31 represents a casing of the pump, a reference numeral 32 designates a partition panel which airtightly partitions a pump chamber 33 from a driving section 34, a reference numeral 35 denotes a shaft which is supported by a supporting member 36, a reference numeral 37 represents a holding member for holding an impeller and a magnet which are disposed rotatably around the shaft 35, a reference numeral 38 designates an impeller which rotates together with the holding member 37, and a reference numeral 39 denotes a follower magnet which rotates together with the holding member 37: all of these members being disposed in the pump chamber 33. In the driving section 34 partitioned with the partition panel 32, a driving magnet 40 which is rotated with a motor 41 is disposed so as to oppose to the follower magnet 39 with the partition panel 32 interposed.
This impeller motor rotates the driving magnet 40 by driving the motor 41 and rotates a follower magnet 39 which is magnetically coupled with the driving magnet 40 by rotating the driving magnet 40. When the follower magnet 39 is rotated, the impeller 38 is rotated to perform a pump function.
By the pump function of the impeller 38, hot water is sucked out of the vessel 30, sucked through a suction port 42 of the impeller pump and discharged from a discharge port 43.
Furthermore, a diaphragm pump is known as a pump which supplies a liquid or the like.
The diaphragm pump has a configuration shown in FIG. 2, wherein a reference numeral 50 represents a motor, a reference numeral 51 designates a crank body which is fixed to an output shaft 50a of the motor 50, a reference numeral 52 designates a driving shaft which is pressed and fixed into the crank body 51 at a location eccentric from the output shaft 50a, a reference numeral 53 denotes a connecting rod which is rotatably coupled with the driving shaft 52 and a reference numeral 54 represents a diaphragm made of a synthetic rubber or the like which is fixed to a tip of the connecting rod. Formed as an outer circumferential portion of the diaphragm 54 is a sealing portion which is sandwiched between a clamp plate 55 and a casing 66 to seal a pump chamber from external air. Furthermore, a reference numeral 61 represents a suction port, a reference numeral 62 designates a discharge port, and check valves 58 and 59 such as leaf valves are disposed in the suction port 61 and the discharge port 62 respectively.
When the motor 50 is driven and its output shaft 50a is rotated, the diaphragm pump which has the configuration described above rotates the crank body 51, the driving shaft 52 moves the diaphragm 54 upward and downward by way of the connection rod 53 and, upward and downward movements of the diaphragm 54 increase and decrease a volume of the pump chamber 60. When the volume of the pump chamber 60 is increased, the leaf valve 58 opens and a fluid is sucked through the suction port 61 and when the volume of the pump chamber 50 is decreased, the leaf valve 59 opens and the fluid is discharged from the discharge port 62, thereby performing a pump function.
When hot water is sucked from a vessel and supplied using an impeller pump such as that shown in FIG. 1, air bubbles are produced in the pump. Since a vapor pressure is lower in the vicinity of a rotating center of the impeller 38, that is, in the vicinity of the shaft 35 in particular than those in other locations in the pump chamber 33, the produced air bubbles are collected in the vicinity of the shaft 35, close the suction port 42 and make the hot water hardly flow, thereby remarkably lowering a hot water supply capability of the pump or disabling the pump from supplying the hot water in a worse case.
Furthermore, the impeller pump which is used for supplying hot water has a defect that the pump requires a high cost since it uses a large number of expensive parts such as two magnets of the driving magnet 40 and the follower magnet 39 as shown in FIG. 1 to maintain sufficient airtightness.
Furthermore, a diaphragm pump such as that shown in FIG. 2 is not disabled from supplying hot water since the pump is capable of exhausting bubbles at a certain degree even when bubbles are produced. However, the diaphragm pump has a defect that it cannot assure a sufficient reliability from a viewpoint of a service life of the diaphragm which is made of the synthetic rubber since a certain kind of synthetic rubber adds an abnormal taste or an abnormal odor to hot water and is hardened dependently on a vapor temperature or the like.
Furthermore, some of diaphragm pumps use metal diaphragms. FIG. 3 shows an example of diaphragm pump using a metal diaphragm 70 as a diaphragm and has a configuration substantially the same as that of the diaphragm pump using the diaphragm made of the synthetic rubber shown in FIG. 2, except for the metal diaphragm 70 which is sandwiched and fixed between a connecting rod 53 and a retainer 71. Accordingly, a pump function of the diaphragm pump shown in FIG. 3 which is similar to that of the diaphragm pump shown in FIG. 2 and is performed by deforming the metal diaphragm so as to change a volume of a pump chamber.
The diaphragm pump which uses the metal diaphragm has a defect that stresses are concentrated on a middle portion of the metal diaphragm (an outer circumference of the connecting rod 53) when the metal diaphragm is displaced largely, whereby this portion is liable to be broken and the diaphragm has an extremely short service life. In order to correct this defect, the diaphragm pump is configured large or when the pump is configured to cause a relatively short displacement of the metal diaphragm, the diaphragm pump has another defect that it cannot exhaust air bubbles sufficiently and lowers a flow rate.
Furthermore, a diaphragm pump disclosed by Japanese Patent Kokai Application No Hei 10-281070 is known as another conventional diaphragm pump.
This pump has a configuration shown in FIG. 4, wherein the pump comprises a pump chamber 74 formed by an upper half 71 of a pump body 70 and a diaphragm 73, a piston 75 attached to a lower half 72 of the pump body 70, and an operating fluid 76 sealed between the piston 75 and the diaphragm 73.
The conventional pump shown in FIG. 4 performs a pumping action by producing a pressure of the operating fluid with an action of the piston 75, deforming the diaphragm 73 with the pressure, and increasing and decreasing a volume of the pump chamber.
Judging from embodiments, this diaphragm pump basically uses a liquid as the operating fluid though description is made that air (a gas) can be used as the operating fluid and the diaphragm pump basically uses a sheet of expansible and contractible synthetic resin such as teflon or synthetic rubber as the diaphragm 73 though description is made that a thin metal plate is used as the diaphragm 73.
When a piston is used for deforming the diaphragm 73 as in this conventional example, it is important to prevent a fluid from leaking and when a liquid is used as an operating fluid in particular, prevention of liquid leakage constitutes an important theme. Accordingly, sealing of a piston section poses a difficult problem and a diaphragm pump has a defect that it is made expensive for complete sealing.
An object of the present invention is to provide a diaphragm pump which comprises a first diaphragm which is operated with a driving mechanism such as a crank mechanism, a second diaphragm disposed so as to form an air chamber between the first diaphragm and the second diaphragm, a pump chamber formed on a side opposite to the air chamber, an inflow port connected to the pump chamber by way of a check valve and an outflow port connected to the same pump chamber by way of a check valve, and is configured to perform a pump function by changing a pressure in the air chamber between the first diaphragm and the second diaphragm with a function of the crank mechanism, deforming the second diaphragm by the change of the pressure and changing a volume of the pump chamber by the deformation of the second diaphragm.
The diaphragm pump according to the present invention distributes stresses uniformly and is not problematic in its durability since the second diaphragm is deformed not directly by the driving mechanism such as the crank mechanism but by utilizing the pressure change in the air chamber even when a metal diaphragm which is resistant to high temperature hot water is used in the pump chamber, that is, even when metal diaphragm is used as the second diaphragm.